Electrode assembly and method for signaling a monitor

ABSTRACT

An electrode assembly adapted to be attached to the skin over selected facial muscle groups picks up signals to be analyzed by an anesthesia adequacy monitor that measures the level of awareness of a living animal, typically a human being. The electrode assembly also includes a stimulator that stimulates a facial nerve to determine the level of paralysis, or neuro muscular block, of the facial muscles. Also disclosed is a method of manufacturing the electrode assembly by printing a pattern of electrically conductive material through a silk-screen or an ink type process onto a flexible layer, and then coating the result with a non-conducting adhesive except at points corresponding to sensing points for the desired muscle groups. Finally, a method for using such sensing and stimulating devices is shown in determining and maintaining an appropriate level of patient awareness, muscle paralysis, and analgesia under anesthesia.

This application is a continuation of U.S. Ser. No. 09/107,098, filedJun. 29, 1998, now U.S. Pat. No. 6,233,472 which is continuation-in-partof U.S. patent application Ser. No. 08/475,024, filed Jun. 6, 1995 nowU.S. Pat. No. 5,772,591, issued June 30, 1998.

FIELD OF THE INVENTION

The following invention relates to devices which are used in the fieldof assessment of consciousness of a person, electromyography, andspecifically for measuring the clinical condition of a patient underanesthesia by noting the muscular activity related to facialmicro-expressions. This invention is also concerned with a method fordetermining the adequacy of anesthesia, and the level of paralysistherefrom, during surgery and otherwise through stimulating andmeasuring the muscular activity of the face. This method and this deviceallows for quick application of stimulating and multiple sensing meansfor the different muscles in the face.

INCORPORATION OF SPECIFICATION BY REFERENCE

U.S. Pat. No. 5,195,531 describing an anesthesia adequacy monitor andmethod, was issued to Henry L. Bennett on Mar. 23, 1993. The disclosureof U.S. Pat. No. 5,195,531 (the “First Bennett Patent”) is specificallyincorporated herein by reference.

BACKGROUND OF THE INVENTION

In the past, when the face was stimulated and monitored for facialexpressions to indicate the depth of anesthesia, individual electrodeswere often applied one at a time. The time required to apply individualelectrodes was significant, especially when a full surgical operatingcrew was standing by or there were patients waiting for their turn inthe surgery operating theater.

Additionally, when individual electrodes are used, there was the problemof multiple wires leading from the patient to any type of signalreceiving device. It was, of course, important to keep track of whichwire was connected to which electrode and where that electrode wasplaced on the face or other part of the patient's body. It was alsoimportant that the wires be hooked into the proper receptacle in anytype of monitor. Again, valuable time was taken up in order to assurethat the wires and electrodes had been properly placed on the patientand into the monitoring device.

In addition, as noted in the Background Of The Invention of the FirstBennett Patent, there has been no adequate by expeditions method ofmonitoring the depth of unconsciousness of a patient under anesthesia.In this regard, anesthesia often seeks to provide a variety of resultsfor the patient during surgery and invasive medical procedures. One suchresult is to provide oblivion through a state of unconsciousness.Another is to provide freedom from pain registration, conscious orunconscious. In seeking to achieve oblivion for the patient, however,the anesthesia can and often does paralyze muscle groups in varyingdegrees from partial paralysis to total paralysis.

In addition to the issues explained about the prior devices and methodsexplained in the First Bennett Patent, the surface electromyogramdevices identified therein did not sense a sufficient number of facialmuscle groups to procure sufficient response data. Similarly, they alsohave not provided a mechanism to readily assess the level of paralysis(neuro muscular blockade) of facial muscle groups brought about byanesthesia and to then quickly process this type of information in orderto yield more accurate indicators of the depth of paralysis of theperson, if any, and also of the depth of unconsciousness of a person inview of paralysis, if any.

As also shown in the prior art cited in the First Bennett Patent and inthis specification, there are many electromyogram devices in the priorart for monitoring neuro muscular blockade during anesthesia (“NMBMs”).Another example of an NMBM is the Datex-Engstrom NeuroMuscularTransmission Module, M-NMT. This NMBM utilizes two stimulator electrodessecured to a patient's wrist, a return electrode secured to thepatient's finger, and a sensor mounted on the patient's thumb to monitorthe hypothenar muscle stimulated by the ulnar nerve. This NMBM is notdesigned for easily and reliably mounting on and sensing facial musclegroups and does not include any means of receiving output from thesensors, calculating and reporting consciousness indicators based on theoutput from the sensors, and also quickly and automatically processingneuro muscular blockade information to more accurately and automaticallymeasure the depth of paralysis, if any, and the depth of consciousnessof a person.

The following disclosures reflect the state of the art of whichapplicant is aware and is included herewith to discharge applicant'sacknowledged duty to disclose relevant information available. It isstipulated, however, that none of these references teach singly norrender obvious when considered in any conceivable combination the nexusof the instant invention as disclosed in greater detail hereinafter andas particularly claimed.

PATENT NO. ISSUE DATE INVENTOR 2,902,030 Sep. 1, 1959 Kennedy et al.3,572,322 Mar. 23, 1971 Wade 3,774,593 Nov. 27, 1973 Hakata et al.3,946,723 Mar. 30, 1976 Servos 4,082,087 Apr. 4, 1978 Howson 4,353,372Oct. 12, 1982 Ayer 4,448,203 May 15, 1984 Williamson et al. 4,583,549Apr. 22, 1986 Manoli 4,763,660 Aug. 16, 1988 Kroll, et al. 5,195,531Mar. 23, 1993 Bennett

OTHER PRIOR ART Including Author. Title, Date, Pertinent Pages, Etc.

Ritchie, G., et al., A Microcomputer Based Controller for NeuromuscularBlock During Surgery, Annals of Biomed. Eng. 13:3-15 (1985)

Edmonds, H. L., et al., Ouantitative Surface Electromyography inAnesthesia and Critical Care, Int J. Clin. Monitoring and Computing3:135-145 (1986)

Chang, T., et al., Continuous Electromyography for Monitoring Depth ofAnesthesia, Anesth Analg. 67:521-5 (1988)

Edmonds, H. L., et al., Objective Assessment of Opioid Action by FacialMuscle Surface Electromyography (SEMG). Prog. Neuro-Psychopharmacol. &Biol. Psychiat. 12:727-738 (1988)

Paloheimo, et al.: Comparison of Upper Facial and Hypothenar Block, J.of Clinical Monitoring 4:256-260 (1988)

Tammisto, T., et al., Assessment of Neuromuscular Block: Comparison ofThree Clinical Methods and Evoked Electromyography. Eur. J.Anaesthesiol. 5:1-8 (1988)

Nielsen, T. A., et al., Effects of Dream Reflection on Waking Affect:Awareness of Feelings, Rorschach Movement, and Facial EMG. Sleep 12(3):277-286 (1989)

Paloheimo, M., Assessment of Anaesthetic Adequacy with Upper Facial andAbdominal Wall EMG. Eur. J. Anaesthiol. 6:111-119 (1989)

Schwilden, H., Surveillance et Conduite de l'Anesthesie a l'Aide del'EEG. des Potentiels Evoques. de l'EMG du Muscle Frontal ou duMonitorage de la Contractilite Oesophagienne Ann. Fr. Anesth. Reanim.8:162-166 (1989)

McAdams, E. T., et al., Designing Biosignal Monitoring Sensors. Sensors,:25-27 (1994)

Datex-Engstrom, NeuroMuscular Transmission Module Product Description,Internet Web Page (1998) (reporting prior art NMBM device byDatex-Engstrom discussed above)

The Kennedy et al. patent, U.S. Pat. No. 2, 902,030, described theelectrodes at the bottom of column 3 as “small discs of sponge rubberwetted with saline solution or small metal disc attached to the surfaceof skin with adhesive tape.” A good contact was provided by applicationof a small amount of “electrode jelly” between the skin and a metalelectrode. The electrodes were applied in the supra orbital region ofthe head of a person. No specific facial muscle group was mentioned.

The Servos patent, U.S. Pat. No. 3,946,723, disclosed attaching a pairof electrodes to opposite temples of a patient for detecting horizontaleyeball movements using the cornea-retina potential. A second pair ofelectrodes attached to brow and cheek bones detected, at a differenttime, the cornea-retina potential showing vertical eye movement.Finally, a ground electrode was attached elsewhere on the face. The datagained was used to diagnose the presence of nystagmus as an indicator ofvestibular disorders. A patient under anesthesia may not have hadreliable eye movements or even any purposeful eye movements at all.

The patent Williamson, et al., U.S. Pat. No. 4,448,203 taught the use ofa device for sensing electrical activity within target muscles such asthe masticatory muscle. One part of the device shown was a pad with twoelectrodes disposed on one side and a grounding electrode disposed onthe other side. The method of use for this device was for the patient tohold the electrode pad up against his face with the two electrodes sidescontacting the face and the one electrode side contacting the finger ofthe holder. Because the patient must hold the electrode device againsthis face, this device was impractical for a patient under anesthesia.

The patent to Manoli, U.S. Pat. No. 4,583,549, disclosed a pad witheither three or six electrodes placed in a fixed precordialconfiguration to assist in obtaining an ECG displaying electricalactivity of the cardiac musculature. The electrodes used were eithersilver plated copper discs with silver/silver chloride eyelets attachedto provide a convenient hook-up point for ECG recording cables, orcopper discs and copper connecting paths to connector edge tab which areetched on the flexible printed circuit board (with conductive gel coatedon the discs and the rest of the board coated with a non conductiveadhesive and release paper). Problems remained with the manufacture ofthe second described electrodes because of the care necessary to assurethat the conducting gel coated only the discs, that the insulating coatnecessary to avoid contact between the circuits and the patient's skinwas completely protective, and the necessity of hooking the sixconductor cable to the connector edge tab.

The patent to Rantala taught the use of a device for measuring the depthof anesthesia which combined a surface electromyogram attached to afacial muscle with an electroencephalogram and an electromyogramattached to a patient's hand. While this application did sense thefacial muscle activity, it interpreted the activity directly rather thanusing surface electromyogram readings to determine a facial expressioncorresponding to the consciousness of the patient, as does theapplicant's device. Furthermore, the applicant's device uses an array ofsurface electromyograms providing a more accurate representation of apatient's facial expression, and hence a more accurate representation ofthe patient's awareness level.

The article by Ritchie, et al. in the Annals of Biomedical Engineering,1985 described the placement of stimulating and recording electrodes onthe wrist and palm of the patient. The electrodes were described as30-gauge needles that were subcutaneously inserted near the ulnar nerve.The recording electrodes were infant EKG surface electrodes.

The article by Edmonds, et al. published in 1986 in the InternationalJournal of Clinical Monitoring and Computing described attachingadhesive skin electrodes over the belly of the frontalis muscle and alsoelectrodes over the temporal bone and mastoid process. This was done forthe purpose of determining the level of a patient's awareness. In alater article by Edmonds, e al. in 1988 in the Prog.Neuro-Psychopharmacol. & Biol. Psychiat. an electrode was placed overthe same belly of the medial frontalis muscle with a reference electrodeplaced over the mastoid process. Again, no more than one muscle groupappears to have been attached to one individual electrode.

The article by Chang is of interest in that it also used a surfaceelectromyogram attached to a facial muscle group andelectroencephalogram data during surgery. However, the method taught inthis article was designed to effectively administer anesthesia andprovided no method for monitoring the awareness level of the patient forpatient comfort as does the instant invention.

The article by Nielsen disclosed using electrode pairs with aninterelectrode distance of 2 cm. center to center. Facial sites selectedfor evaluating REM sleep were right and left corrugator supercilli (forsadness brow-knitting motion) and right and left zygomaticus major (forhappiness smiling). The readings were used to judge feeling-specificmotor activity during imagery reflection of REM sleep, not awarenessduring anesthesia.

The article by Paloheimo in the 1988 Eur. J. Anaesthiol, told of usingsurface electrodes in pairs to record facial electromyographic activity.The first pair was attached on the forehead 3 cm above the mid-eyebrowand on the mastoid process, with a ground electrode on the temporalarea. A second pair was located on the mamillary end anterior axillarylines 10 cm. apart within the left dermatomes, with a ground electrodeon the external iliac process. No assembly of electrodes to saveapplying electrodes one at a time was discussed.

The second article by Paloheimo in the J. of Clinical Monitoringdescribed attaching one pair of recording electrodes in the midline ofthe forehead and above the mid portion of an eyebrow for recordingelectrically evoked muscle potentials. Stimulation was provided byattaching a different pair of stimulating electrodes, one just posteriorto the lower part of the pinna and the other just anterior to thetragus. The facial muscle stimulated were procerus, frontalis,corrugator, and orbicularis oculi muscles. No mention was made ofrecording the patient's unstimulated state.

The article by McAdams, et al. published in 1994 discussed how flexiblesubstrates have been printed with thin layers of silver loaded ink toserve as electrodes. Also discussed was how a tab of a conductive sensorextended beyond the portion of an electrode coated with a solid,conductive adhesive hydrogel and was adapted to be connected to amonitor cable with an alligator clip. However an assembly having morethan one electrode was not discussed.

The device and method of this application more effectively achieves thepurpose of providing for quick and sure attachment of electrodes to thetissue of a living animal, especially the face of a human patientundergoing surgery. The electrode assembly can, when serving as thesensing means for picking up signals through the skin of facial musclegroups, provide an anesthesiologist with a reliable indicator of thepatient's awareness level when the patient is otherwise uncommunicative.One particularly preferred embodiment of the assembly has sensors forpicking up signals of five different facial muscles and further includesNMBM stimulators and sensors to reliably and more easily monitor neuromuscular blockage (paralysis) of the patient.

The device and method of this application also more easily, readily,economically, and effectively senses one or more facial muscle groups,assesses the level of paralysis of facial muscle groups, processes theparalysis information in order to promptly indicate the paralysis leveland the depth of unconsciousness of a person in view of paralysis, ifany.

SUMMARY OF THE INVENTION

The applicant's preferred device provides a convenient, effective, andeconomical electrode assembly for monitoring differential electricalstates in various parts of a living animal. Preferably, the electrodeassembly can be used for simultaneous monitoring of the nerve signals tofacial muscle groups to reflect the patient's facial muscle tonus, whichcan be used as a reliable indicator of the level of awareness for thepatient while under anesthesia. In one embodiment, the electrodeassembly, especially when it includes at least three electrodes,preferably five electrodes, can be used to monitor the differencebetween two muscle groups. In yet another embodiment, the electrodeassembly includes thirteen electrodes to monitor five muscle groups andstimulate, and monitor the resulting effect on, at least one of themuscle groups.

The preferred electrode assembly has a pattern of electricallyconductive material printed on a flexible layer, and also anon-conductive adhesive, which serves to isolate electrodes from eachother. The assembly is adapted to follow the facial contours of apatient. Also the electrode assembly, by having a substantially uniformthickness, prevents pressure points from developing when the electrodeassembly comes between the living animal tissue and any support surfacesuch as an operating table or bed pillow.

Using the electrode assembly as a sensing means for judging the state ofpatient awareness, an anesthesiologist can better control and providegreater comfort for a patient undergoing anesthesia during the course ofsurgery. Specifically, the electrode assembly allows quick and sureattachment and a preconfigured pattern for applying the electrodes overselected facial muscle groups. The design of the electrode, with thetrailing ribbon attached to the electrode sensing points in an unbrokenelectrical pathway, allows a monitor or other signal processing deviceto receive what the electrodes have picked up. After processing thesignals using one or more algorithms, the anesthesiologist may view adisplay representing the patient's face or other indicators derived fromthe processed signals. Based upon this information, the anesthesiologistthen can control the dosage of anesthetic to reach the desired level ofpatient awareness, paralysis, and analgesia. These are all doneindependently with different drugs based on the three signals fromFACE-level of a) awareness, b) paralysis, and c) analgesia.Additionally, the signal processor can be informed of artifactgenerating events which can be subtracted out from the signal receivedby the processor or monitor. This allows the surgeon to use such devicesas an electric cauterizer during the course of surgery withoutinterfering with the anesthesiologist efforts to maintain a desiredlevel of patient awareness.

Fabrication of the electrode assembly can be based upon a silk-screenprinting method, but preferably an ink type printing process is used. Aflexible layer, which is characterized by resisting linear distortion,is printed with a pattern of electrically conductive material. Over thispattern is placed non-conductive adhesive either in the form of apre-shaped pad with apertures allowing for contact with the livingtissue of the animal through an electrolytic medium, or the pattern ofelectrically conductive material is coated with a non-conductiveadhesive except at points where pads prevent coating and such pointscorrespond to sensing points on the animal. A detachable layer over theelectrode area can preserve the electrode assembly during shipping.

In designing the preferred pattern of electrically conductive materials,the locations of the Corrugator and Frontalis muscle groups can be takeninto consideration for one set of electrodes and stimulators, as well asthe Zygomatic, Orbicularis Oculi, and Masseter facial muscle groups inthe case of a second group of electrodes. Finally the ribbon trailingoff the area of contact between the electrodes and tissue can be adaptedat the opposite end to be engaged by the prongs of a spring-biasedsignal input clamp, or preferably a mechanical clamping ZIF connector.

The electrode assembly can thus be attached to a processor to processoutput from the sensing electrodes according to predetermined analysisprograms or algorithms. The processor can be attached to a display orother device reporting or utilizing output from the processor in orderto monitor the consciousness, paralysis, or analgesia of the person towhom the electrode assembly is attached.

Preferably, the electrode assembly includes stimulators for stimulatingthe upper branch of the facial nerve and recording the response at theCorrugator facial muscle preferably through the use of non-invasive,interferential stimulation. Upon stimulation, the sensors at theCorrugator facial muscle area indicate the response of that muscle areaand thus provide an indication of the level of paralysis, if any(including undesirable total paralysis rendering the facial musclesincapable of micro-movements and the attendant indications awareness orstress information). Partial paralysis information can be used by theprocessor to adjust paralysis-affected monitoring of the facial musclesensors, such as monitoring pursuant to sensor summation algorithms toreport the awareness of the monitored person. As long as the paralysisis not total, the processor can also apply, and report the outcome of,other methods of analysis, such as sensor differential or ratioalgorithms that report the stress or pain registering with the personbeing monitored.

There are other aspects of the invention that will become apparent asthe specification proceeds below.

OBJECTS OF THE INVENTION

Accordingly, it is an object of the present invention to provide adevice which allows for quick and accurate placement of electrodes uponthe tissue of a living animal to monitor differential electrical states.

Another object of the present invention is to provide an electrodeassembly which is easily and economically manufactured by well-knowntechniques such as silk-screen or ink type printing process.

Another object of the present invention is to provide a sensing meanspreconfigured to pick up signals from certain facial muscle groups thatwill serve as a reliable indicator of the level of awareness of apatient undergoing anesthesia wherein the same preconfigurationarrangement of electrodes can be used with different individuals.

A further object is to provide stimulators, preferably of thenon-invasive type and mounted within the electrode assembly, forstimulation of a facial nerve and measurement of the responsivemovement, if any, of the stimulated facial muscle.

A related object is to have the stimulating and sensing means sense thelevel of paralysis, of any, of the facial muscles.

Yet another object of the present invention is to provide for anelectrode assembly of substantially uniform thickness which assures thatwhen the assembly is in between the patient's tissue and a bed pillow ormattress or surgery table that no pressure points are developed duringthe monitoring of the patient.

Another object of the present invention is to provide a method forinforming an anesthesiologist of the level of patient awareness throughthe use of an electrode assembly which picks up signals from facialmuscle groups which can be processed to provide a display representingthe patient's facial muscle tonus, the display can be used by theanesthesiologist to monitor the patient's level of awareness and respondthereto with differing dosages of anesthetic and/or level of analgesia.

Viewed from a first vantage point it is the object of the presentinvention to provide an electrode assembly for monitoring differentialelectrical states in various parts of a living animal, comprising: aflexible layer, a pattern of electrically conductive material, disposedupon one side of the flexible layer wherein the pattern contains atleast two electrodes and is adapted to be connected to a signalreceiving means, and a non-conducting adhesive that electricallyisolates at least one electrode from another electrode, but allows atleast two electrodes to contact the tissue of the living animal.

Viewed from a second vantage point it is the object of the presentinvention to provide a method for maintaining an appropriate level ofpatient awareness under anesthesia, the steps including: providing atleast one electrode assembly, comprising a flexible layer, a pattern ofelectrically conductive material, disposed upon one side of the flexiblelayer wherein the pattern contains as at least two electrodes and isadapted to be connected to a signal receiving means, a non-conductingadhesive that electrically isolates at least one electrode from anotherelectrode, but allows at least two electrodes to contact the tissue ofsaid patient; and attaching the assembly to the face of the patient,picking up a signal with the electrodes, receiving the signal in aprocessing device through a signal receiving means, processing thesignal received from the electrodes to determine what facial expressionthe signal represents by comparing the signals from differentelectrodes, the signals being reflective of the patient's facial muscletonus, displaying the processed signal for viewing by ananesthesiologist on a display, anesthetizing the patient with an initialdosage of anesthetic to create muscle relaxation in a desired level ofawareness, and controlling the patient's level of awareness andanalgesia.

Viewed from a third vantage point it is the object of the presentinvention to provide a sensing means adapted to signal an awarenesslevel detector for informing an anesthesiologist of the level ofawareness of a patient under anesthesia through detection of thepatient's facial expression comprising, in combination: a flexiblelayer, a pattern of electrically conductive material, disposed upon oneside of the flexible layer wherein the pattern contains as at least twoelectrodes and is adapted to be connected to a signal receiving means, anon-conducting adhesive that electrically isolates at least oneelectrode from another electrode, but allows at least two electrodes tocontact the face of said patient.

Another object is to provide a device and method that stimulates andsenses micro-motion in facial muscles in order to: (i) determine andreport the level of paralysis of the muscles; (ii) adjust awarenessdetermining algorithms to continue to adequately report the awareness orconsciousness of a person despite partial paralysis; (iii) report thelevel of pain or stress registering with a person; and (iv) provideinformation about awareness, paralyzation, and stress or pain so thatanesthesia may be more appropriately administered to procure the desiredoutcome and minimization or elimination of pain, stress, andconsciousness of a patient during surgery, for example.

These and other objects of the present invention, such as those setforth in the First Bennett Patent, will be made manifest whenconsidering the following detailed specification when taken inconjunction with the appended drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective drawing of a two-muscle-area electrode assemblyas engaged with a spring biased signal receiving clamp.

FIG. 2 is a perspective drawing showing the two-muscle electrodeassembly being engaged by the spring biased signal receiving clamp.

FIG. 3 is a representation of the first step fabricating the two-muscleelectrode assembly wherein electrically conductive material is appliedto the flexible layer.

FIG. 4 is the second step in the fabrication of the two-muscle electrodeassembly wherein non-conductive adhesive is applied to the result of thefabrication step shown in FIG. 2.

FIG. 5 is a perspective view of an alternate second step wherein apre-formed shape of non-conductive adhesive is about to be mated withthe result of the fabrication step shown in FIG. 2.

FIG. 6 is a perspective view of the third step in the fabricationprocess wherein a detachable pad is applied to the result of the secondstep of the fabrication process.

FIG. 7 is a cross section view of the two-muscle electrode assemblytaken along line 7—7 of FIG. 1.

FIG. 8 is a perspective view of the two-muscle electrode assembly beingapplied to the person's face after application of an electrolytic mediumto the electrode contact points.

FIG. 9 is a front plan view of two two-muscle electrode assembly devicesof this application in place on a person's face.

FIG. 10 is a block diagram representing the relationships of the stepsof method of this application for sensing four facial muscle areaswithout active stimulation by the electrode assembly.

FIG. 11 is a block diagram representing the fabrication steps involvedin manufacturing the electrode assembly devices of this application.

FIG. 12 is a partial perspective view of an alternative unitaryelectrode assembly, applied to the person's face, having electrode's forsimultaneously sensing motion of five facial muscle areas as “Train ofFour” and tetanic constant current nerve stimulation. However, thisdevice may stimulate the nerve by interferential stimulation (i.e.,applying two higher frequencies in order to obtain a low differentialfrequency for stimulation of the nerve).

FIG. 13 is a block diagram representing the relationships of thepre-surgery steps of the alternative method of this specification forsensing five facial muscle areas and actively stimulating a muscle areawith the five-muscle electrode assembly.

FIG. 14 is a block diagram representing the relationships of the stepsof the alternative method of this specification for sensing five facialmuscle areas and actively stimulating a muscle area with the five-muscleelectrode assembly during surgery.

FIG. 15 is a block diagram representing the general relationships of theelements of the alternative device and method of this application forsensing five muscle areas and stimulating one muscle area.

FIG. 16 is a plan view of one possible output for display in thealternative device of this application for sensing five muscle areas andstimulating one muscle area.

DESCRIPTION OF PREFERRED EMBODIMENTS

Considering the drawings, wherein like reference numerals denote likeparts throughout the various drawing figures, reference numeral 10 isdirected to a two-muscle electrode assembly according to the presentinvention. Referring now to FIG. 1, an electrode assembly 10 is shownengaged with spring biased signal input clamp 18. Leading from electrodecontact points 12 are electrical connecting paths 14 which carry anysignal received by electrode contact points 12 to spring biased signalinput clamp 18. The electrode contacts points 12 and electricalconnecting paths 14 are disposed upon flexible layer 24. Flexible layer24 can be made from any of a number of flexible plastic substrates.Depending on the type of plastic used, the thickness of the flexiblelayer can vary from 1 mil to 3 mil, preferably being 2 mil for preferredplastic. A preferred embodiment of electrode assembly 10 uses one typeof plastic that is a combination of vinyl and mylar plastics. Going onnow to FIG. 2, spring bias signal input clamp 18 is shown with the jawsopen ready to receive electrode assembly 10. The ribbon of the electrodeis guided into the proper position in the jaws of the clamp 18 by guides19. Contact points 20 engage individually, each one of the electricalconnecting paths 14 because the electrical connecting paths 14 have beenspaced apart a proper distance to ensure engagement with only onecontact point 20 of spring biased signal input clamp 18. FIG. 1 does notshow the electrode assembly in a perspective view of actual use, it isfor illustration purposes alone. It is contemplated that the electrodeassembly 10 would first be placed upon the living animal tissue, such asa patient's face, before being hooked up to spring biased or ZIF typesignal input clamp 18. Of course, it is to be understood that othermethods of engagement for electrode assembly 10 could be used to carrythe signal picked up by electrode assembly 10 and deliver it to a signalprocessor.

Referring now to FIG. 3, the flexible layer 24 is shown as beingprepared to receive the electrically conductive material 16 that makesup electrical connecting paths 14 and electrode contact points 12.Electrically conductive material 16 is carried to mask means 22 bysqueegee 26. Mask means 22 can be a silk-screen used in a silk-screenprinting process or an ink type process. As shown, mask means 22contains openings 28 that allows electrically conductive material 16 insqueegee 26 to flow through onto flexible layer 24 when mask means 22 islowered into contact with flexible layer 24.

After allowing the electrically conductive material to dry, the flexiblelayer 24, with a pattern of electrically conductive material 16displayed thereon one side, can be treated in various ways to completethe fabrication of electrode assembly 10. As shown in FIG. 4, buttons 30are placed over the electrode contact points 12. Then, non-conductiveadhesive 32 is sprayed onto a side of the flexible layer 24 with thepattern of electrically conductive material 16. These buttons 30 areshown as being put into engagement with the electrode contact points 12.The electrode contact points 12 will match up with later locations onthe skin of the animal. Typically the locations are placed so that theelectrode contact points 12 can pick up signals from the desired musclegroups. Non-conductive material 32 is now applied by spray gun 34 tocoat the entire surface of flexible layer 24 including electricallyconductive material 16 and buttons 30. After the material has beensprayed on, the buttons 30 do not adhere to the electrode contact points12. This allows easy removal of any non-conductive material from thearea over the electrode contact points 12, especially if anon-conductive material 32 has been scored over the perimeter ofelectrode contact points 12.

Other methods of applying non-conductive material 32 can include asecond silk-screen printing similar to FIG. 3. The non-conductivematerial 32 is preferably applied using a printing roller without anymask means, as long as buttons 30 are used. However the non-conductivematerial 32 is applied to flexible layer 24, it is necessary to ensurethat the electrically connecting paths 14 and electrode contact points12 do not come into contact with each other. If allowed to, this couldwell short out the pathway for delivering the signal received to theprocessor unit.

Another way to apply the non-conductive material 32 to flexible layer 24with electrically conductive material disposed on one side is for apre-formed shape, like a pad, to be placed over the flexible layer 24with electrically conductive material 16 on one side as shown in FIG. 5.Within this pre-formed layer, at the appropriate spots over theelectrode contact points 12, are apertures 38, preferably filled with anelectrolytic medium 40 seen later in FIG. 7 such as lanolin based creamcontaining electrolytes (such as Signa Creme 1705 available from ParkerLaboratories). When applied to the tissue of a living animal, theapertures allow signals to be received by electrode contact points 12,especially if an electrolytic medium is used. Because the layer ispre-formed, mating it with the pattern of electrode contact points 12 onflexible layer 24 should not require much micro-adjustment of thelocation.

Referring now to FIG. 6, flexible layer 24 with electrical connectingpaths 14 and electrode contact points 12 and non-conductive material 32applied is ready for mating with detachable pads 42. As can also be seenin FIG. 6, electrode assemblies 10 are often produced in multiplenumbers on a single flexible sheet 24. After detachable pads 42 aremated with the electrode assemblies 10, the assemblies 10 can beseparated. Separation can be done through use of a knife, scissors, orother appropriate cutting means. As can be observed in FIG. 6, theelectrode assemblies are sometimes mirror images of each other. Also,depending upon the muscle groups that the user may wish to monitor,electrode assemblies 10 can assume different configurations for theirelectrode contact points. Although FIGS. 3, 4 and 5 show only thepreparation of a single electrode assembly, the silk-screen mask 22 canhave many electrode assembly patterns present and a number of electrodeassemblies 10 can be printed onto a flexible layer 24.

Referring now to FIG. 7, the electrode assembly 10 is seen in crosssection. Flexible layer 24 accounts for much of the thickness of theassembly 10. Differing electrical connecting paths 14 and the electrodecontact points 12 are also present. The space above contact points 12 isvacant, while non-conductive adhesive 32 is above other parts offlexible layer 24. At the far right, the space above contact point 12 ispre-filled with electrolytic medium 40. However, the substantiallyuniform thickness of electrode assembly 10 is preserved due to thethinness of the non-conductive adhesive 32. Thus, the presence orabsence of non-conductive adhesive 32 does not radically change thethickness of electrode assembly 10. Therefore, when electrode assembly10 is between the tissue of a living animal and a support means, such asan operating table a pillow on a bed, then substantially uniformthickness prevents any point from becoming a pressure point. The lack orpressure points in electrode assembly 10 when so used prevents thedevelopment of sores and other discomfort for the patient.

Referring now to FIG. 8, a patient's face is prepared to receiveelectrode assembly 10 which has no electrolytic medium packaged with it.It is preferred to use pre-jellied electrodes in large-scalemanufacturing. An electrolytic medium 40 such as Signa brand creme,could also be applied to the electrode assembly, if the assembly is notprovided with a medium already in contact wells over control points 12.This medium 40 comes in the form of a thick lotion. The medium ispreferably thick enough to hold a bead shape in the well of theelectrode contact point. Other electrode assemblies 10 can be suppliedwith the medium in the well, before the detachable pads 42 are mated tothe flexible layer 24. Other electrolytic mediums 40 such as electrodepaste with adhesive characteristics can be applied to the electrodeassembly 10. The skin over the orbicularis oculi 48 muscle group and thezygomatic 50 muscle groups in FIG. 8 is shown as ready to receive theelectrode assembly 10. FIG. 8 also shows electrode assembly 10 beingpositioned to be applied to the patient's face over the muscle groupswhose monitoring is desired. In a similar fashion, other muscle groupscan have electrolytic medium 40 put into the contact points wells, andthen electrode assemblies 10 applied.

Now referring to FIG. 9, two-muscle electrode assemblies 10 have beenapplied to different areas of a human face. The uppermost assembly 10 isapplied to the corrugator 44 facial muscle group and the frontalis 46facial muscle group. For the lower electrode assembly, the orbicularisoculi 48 facial muscle group is contacted by the upper half of theelectrode. The lower inner electrode contact points are over thezygomatic facial muscle group 50. Ground electrodes 52 are also presentin each electrode assembly 10 shown in FIG. 3.

After applying the electrode assembly 10 with the electrolytic medium 40in the electrode contact point wells, the heat of the patient's skincauses some mediums, such as the aforementioned Signa creme to partiallyliquefy and flow into the patient's sweat glands. This flow establishesbetter electrical contact and hence the electrode assembly 10 can betterpick up the nerve impulses to the target muscle groups. If theelectrotytic medium 40 does not liquefy, sometimes the patient's sweatglands produce perspiration which establishes a better electricalpick-up of nerve signals.

Referring now to FIG. 10, in use and operation the awareness levelmonitor receives signals from electrode assembly 10 placed upon the faceof the patient. The monitor may be used by an anesthesiologist or otherqualified operator to maintain the appropriate level of patientawareness during surgery. Finally, the anesthesiologist confirms theelectrode assembly proper placement on the face of the patient. Baseline reading may be then established. The patient is then givenanesthesia appropriate for the circumstances. The anesthesiologist maythen monitor the display 54 to determine the patient's level ofawareness as reflected in changes in the muscle tonus. Once surgerybegins, the anesthesiologist may use the display 54 to monitor themagnitude of the patient's response to what otherwise would be anobjectively painful surgical stimulus. If the display 54 demonstrates anunacceptably high level of awareness and/or registration of pain, theanesthesiologist may administer more anesthesia or take other correctiveaction. If the display 54 demonstrates an unacceptably low level ofawareness, other corrective measures may be taken. In this way thepatient's comfort may be maximized and the patient's reaction to thesurgical procedure and therefore recovery time can be minimized.

Also necessary to have a accurate display 54 is the removal of artifactsin the signal caused by such artifact generators as electric cauterizingdevices. When this device is used, some electric current flows throughthe patient causing an anomaly in the signals as read by the electrodecontact points 12. The artifact detector connected on one end to thecauterizing device or other artifact generator and on the other end to afirst signal conduit. When an artifact is detected by the artifactdetector, the detector then filters out the portion of the first signalrepresenting the artifact.

Referring now to FIG. 11, a block diagram showing the manufacturingmethod for providing an electrode assembly is displayed. The first step,as previously shown in FIGS. 3, 4, 5, and 6, is to provide anon-extensible material to serve as flexible layer 24. The next step isto apply electrically conductive material 16 through mask means 22 toflexible layer 24. After this is accomplished, the next step is to coatwith a non-conducting adhesive 32, preferably through a mask means. Ashas been previously discussed this is one method. Other methods mayinclude mating a pre-formed layer with the flexible layer 24 withattached pattern of electrically connecting paths 14. The next step isfor a detachable pad 42 to be engaged with the now non-conductingadhesive coated flexible layer. Finally, if there are more than oneelectrode assemblies 10 on the flexible layer 24, the material must becut so that the individual assemblies 10 can be separated.

Referring now to FIG. 12, an alternative electrode assembly orsensor-stimulator array 100 is shown as applied to a patient's face F tosense five muscle groups and stimulate at least one of the themaccording to the alternative method of this specification. This unitaryand integrated sensor-stimulator array 100 is manufactured generallyusing the same techniques described above for the alternative two-muscleelectrode assembly 10. The sensor-stimulator array 100 is, however,easier to apply and maintain in place on the face F of the patient thanis the combination of two two-muscle electrode assemblies described inthe First Bennett patent.

The array 100 has a first sensor 102, a second sensor 104, a thirdsensor 106, a fourth sensor 108, a fifth sensor 110, a ground sensor112, and a stimulator electrode 114. The first, second, third, fourth,and fifth sensors 102, 104, 106, 108, and 110 are mounted over theFrontalis, Corrugator, Orbicularis Oculi, Zygomatic, and Masseter musclegroups, respectively. The first through fifth sensors 102, 104, 106,108, 110 each have two electrodes or electrode sensors, each suchpairing being denoted as + or − in the numbering for the particularelectrode pair (e.g., 102+and 102− as the pair for the first orFrontalis sensor 102).

The first through fifth sensors 102, 104, 106, 108, 110 and groundsensor 112 are generally constructed as described the First BennettPatent. As a result, each sensor 102, 104, 106, 108, 110 and groundsensor 112 collectively generate, as shown in FIG. 15, the collectivefive-muscle signal or group of signals 115 of this alternativemonitoring device, generally 113, and method. The five-muscle signal 115is then passed through a pre-amplifier 27 and processed in generally thesame fashion as described in the First Bennett Patent with themodifications and additions described herein.

Referring back to FIG. 12, the stimulator sensor 114 of this alternativeembodiment 100 utilizes stimulator electrodes or electrode sensors 114Hand 114L to stimulate the upper branch of the facial nerve for recordingat the Corrugator muscle in the patient's face F. (Alternatively, thestimulator sensor 114 could instead consist of a muscle sensor such asone of the first through fifth muscle sensors 102, 104, 106, 108, 110.)By this device and method, the facial muscle nerve lying under thesurface of the skin can be activated without trauma to the nerve ortissues of the patient. The stimulator sensor 114H, 114L is connectedto, as shown in FIG. 15, a stimulator activation device 116 of the typewell known in the art. Upon temporary suspension of recording ofelectromyograms by the monitoring device 113, the stimulator activationdevice 116 can be activated by an operator or anesthetist (not shown) topreferably carry to the patient's face F through the stimulator sensor114 four equally spaced electrical pulses 50 microseconds in durationeach presented as a square wave at a frequency of 2 Hz. Optionally, andreferring to FIG. 12, the pulses on the first stimulator electrode 114Hhave a carrier frequency of 10,050 Hz, and the pulses on the secondstimulator electrode 116L have a carrier frequency of 10,000 Hz. In thisembodiment, one of the two sensors serves as the electrical return forthe current. The two high difference frequencies delivered by stimulatorsensors 114H, 114L stimulate the Corrugator nerve at the much lowerinterferential frequency generated between them, 50 Hz. The highdifference frequencies of the stimulator sensors 114H, 114L penetratebiological tissues more effectively than lower frequencies but are noteffective at stimulating muscles within the tissues. The resultinginterferential low-frequency 10 Hz pulses delivered to the Corrugatornerve are highly effective at stimulating nerves such as the Corrugatornerve deep under the skin of the patient's face F.

Immediately after such stimulation, the second sensor 104 records astimulation signal based on the level of resulting activity in theCorrugator muscle area in the face F. As shown in FIG. 15, thisstimulation signal is transmitted to the computer 60, which records thesignal, processes it according the algorithms loaded in the computer 60,and generates a display of the level of activity on the display 80.

Upon resumption of the recording of electromyograms by the monitoringdevice 113, the five-muscle activity signal 115 is again transmitted topre-amplifier 27, through the detector 40, and into the computer 60. Thecomputer applies an “Aware” and a “Stress” algorithm to the signal 115and creates a second signal 120. This second signal or group of signals120 represents, and causes the display 80 to show: (1) the facialexpression of the patient P such as described in the First BennettPatent; and/or (2) as shown in FIG. 16, a graphical representation ofthe activity sensed for each of the five facial muscle areas and a“Stress” and “Aware” index.

The “Aware” algorithm for determining the “Aware Index” is a summationindex using the following formula:

O+F+C+Z=“Aware Index”

Where:

O is the muscle tonus of Orbicularis Oculi muscle,

F is the muscle tonus of the Frontalis muscle,

C is the muscle tonus of the Corrugator muscle,

Z is the muscle tonus of the Zygomatic muscle, and

The “Stress” algorithm for determining the “Stress Index” is adifferential or ratio based index, preferably using the followingformula with the same nomenclature as set forth above:Stress  Algorithm   $\begin{matrix}{\left. a \right)\quad} & {{{{IF}\left\lbrack {O \geq Z} \right\rbrack}\quad {{or}\quad\left\lbrack {O < {Z\quad {and}\quad C} \leq F} \right\rbrack}},{then}} \\\quad & {{Stress} = {\left( \frac{\left( {C - F} \right) + \left( {O - Z} \right)}{C + F + O + Z} \right) \times 100}} \\\left. b \right) & {{{{IF}\left\lbrack {O < Z} \right\rbrack}\quad {{and}\quad\left\lbrack {C > F} \right\rbrack}},{then}} \\\quad & {{Stress} = {\left( \frac{\left( {C - F} \right) + \left( {M - Z} \right)}{C + F + M + Z} \right) \times 100}} \\\left. c \right) & {M\quad {is}\quad {displayed}\quad {separately}\quad {in}\quad {all}\quad {cases}\quad {as}\quad M}\end{matrix}\quad$

The Aware algorithm and resulting index provides a measure of the degreeof patient oblivion and unconsciousness. However, because this algorithmis a summation of muscle tonus values which will diminish due to muscleparalysis brought about by anesthesia, the Aware Index should becalibrated to adjust for the level of paralysis of the facial muscles.This is accomplished by having determined an original unparalyzedCorrugator stimulator signal, as described above, prior toadministration of anesthesia. Upon administration of anesthesia, asubsequent Corrugator stimulator signal is determined, again accordingto the method described above. The degree of paralysis of the facialmuscles is measured by the percentage change of the stimulator signalfrom the unparalyzed to the anesthetized state. Since muscle activity isinversely proportional to the degree of paralysis, the computer 60multiplies the Aware value calculated during stimulation underanesthesia, at that particular point in time, by the inverse of theremaining level of activity as compared to the original, unparalyzedstate, except in the event of total paralysis when the remainingactivity level is null. Thus, if the Aware value calculated bystimulation during anesthesia is 5% as great as that calculated beforeapplying anesthesia, the computer 60 multiplies the Aware value duringanesthesia at that point in time by a factor of 20 and displays theresulting Aware Index on the display 80. In the event that the remainingactivity level is null, the computer 60 generates an Aware Index ofzero.

This method of stimulation and comparison of muscle activity from thepre-anesthesia to the anesthetized state thus provides a monitor formore precise titration of anesthetic agents during administration ofanesthesia. In addition, in the event of total paralysis or neuromuscular block of the facial muscles, the Aware Index will be zero andthe resulting display of a zero value for the Aware Index on the display80. The anesthesiologist is thus alerted to the state of total paralysisof the facial muscles as well as the inability to rely on anymeasurement of muscle activity ill the face to indicate the patient'strue level of consciousness in view of the total paralysis of the facialmuscles.

Except in the case of total paralysis indicated by the zeroing of theAware Index, the Stress algorithm provides a signal based on the outputfrom the lower brain centers of the basal ganglia and limbic systemsdirectly to the patterning of facial muscles. These signals, known asfacial expressions, are the result of the combination of patientarousal, pharmacological and anesthetic drug states, and surgicalstimulation. By providing a Stress Index based on these signals, theanesthesiologist is provided with an indicator of the true state ofanalgesia and a significant tool for more precise titration of analgesicagents.

In use and operation, the consciousness or anesthesia adequacy monitor10 may be used by an anesthesiologist or other operator to monitorand/or maintain patient consciousness as desired during administrationof anesthesia as suggested in FIGS. 13 and 14. Initially, theanesthesiologist configures the sensor array (100 in FIG. 12) on theface F of the patient P. Referring now to FIG. 14, the patient P is thegiven anesthesia appropriate for the circumstances. As shown in FIG. 13,a base line reading may then be established, including stimulation ofthe facial muscle to determine the response level of the facial musclesin the completely unparalyzed state. The anesthesiologist may thenmonitor the display 80, and as desired stimulate the patient's facialnerve, to determine the patient's level of paralysis and consciousnessas reflected by changes in muscle tonus reported on the display 80. Thedevice preferably includes an automatic mode to stimulate at regularintervals. Initial calibration in the anesthetized, but unparalyzedstate, then rapid repetitions for 5 minutes every 15 seconds, then onceever 4-5 seconds thereafter using the “train of four” method previouslydescribed. Once the surgery begins, the anesthesiologist may use thedisplay 80 to monitor the magnitude of the patient's response tosurgery, including my intermittent stimulation of the patient's facialnerve. If the display demonstrates an unacceptably high level of patientawareness, or total paralysis of the facial muscles, theanesthesiologist may take corrective action. In this way, the patient'scomfort can be maximized and the patient's reaction to surgery, andtherefore the patient's recovery time, can be minimized.

As also noted in the First Bennett Patent, the consciousness monitoringdevice 10 may also be used with a patient who has suffered injury and isexperiencing a diminished level of consciousness. The device 10, orportions thereof, may also be used in other settings in whichconsciousness monitoring is desired. The device may be used as well inICU for titrating sedation, analgesia and/or paralysis.

Moreover, having thus described the invention, it should be apparentthat numerous structural modifications and adaptations may be resortedto without departing from the scope and fair meaning of the instantinvention as set forth hereinabove and as described hereinbelow by theclaims.

We claim:
 1. A method of determining the consciousness of a person, the method comprising the steps of: (A) mounting at least four facial muscle activity sensors so that each activity sensor generates an activity signal based on the level of activity of a different facial muscle group on the person; and (B) processing said activity signals to generate a first output signal based on the summation of the activity signals for the sensed facial muscle groups; and also including in step (B): processing said activity signals to generate a second output signal based on the differences between the activity signals for the sensed facial muscle groups; and also including in step (B): filtering the activity signals to remove from the at least one output signal an artifact representing muscle activity caused by stimulus to the person not indicative of the person's consciousness; and wherein, in step (A), five facial muscle activity sensors are mounted, respectively, on the following five muscle areas: the frontalis area, the corrugator area, the zygomatic area, the masseter area, and the orbicularis oculi area.
 2. An electrode assembly for an awareness level monitor, comprising in combination: (A) a flexible layer; (B) a plurality of electrodes oriented in fixed positions and integrally formed with said flexible layer; (C) plural electrical connecting paths disposed on said flexible layer extending from said plural electrodes to an input of the awareness level monitor, with each said electrode having its own said path; said electrodes being located in at least four sensor clusters of fixed arrays to respectively sense muscle activity of separate facial muscle areas pre-selected from among the frontalis area, the corrugator area, the zygomatic area, the masseter area, and the orbicularis oculi area.
 3. The assembly of claim 2 wherein said electrodes also having a stimulator cluster to stimulate a nerve in at least one of said separate facial muscle areas.
 4. An electrode assembly for an awareness level monitor, comprising in combination: (A) a flexible layer; (B) a plurality of electrodes oriented in fixed positions and integrally formed with said flexible layer; (C) plural electrical connecting paths disposed on said flexible layer extending from said plural electrodes to an input of the awareness level monitor, with each said electrode having its own said path; said electrodes being located in at least (i) two sensor clusters of fixed arrays to respectively sense muscle activity of separate facial muscle areas pre-selected from among the frontalis area, the corrugator area, the zygomatic area, the masseter area, and the orbicularis oculi area; and (ii) a stimulator cluster to stimulate a nerve in at least one of said separate facial muscle areas.
 5. The assembly of claim 3 wherein said electrodes also include a ground electrode providing a grounding path for the sensing clusters.
 6. The assembly of claim 4 wherein said electrodes also include a ground electrode providing a grounding path for the sensing clusters and stimulating cluster.
 7. The assembly of claim 2 including an artifact filtration device for removing anomalous surgically induced artifacts, said filtration device being coupled between said electrical connecting paths and said input of the awareness level monitor.
 8. The assembly of claim 4 including an artifact filtration device for removing anomalous surgically induced artifacts, said filtration device being coupled between said electrical connecting paths and said input of the awareness level monitor.
 9. The assembly of claim 6 including an artifact filtration device for removing anomalous surgically induced artifacts, said filtration device being coupled between said electrical connecting paths and said input of the awareness level monitor.
 10. The assembly of claim 9 wherein said flexible layer is linearly non-extensible along said electrical paths to thwart breaks in conductivity along said paths.
 11. The assembly of claim 10 including an adhesive coating on said flexible layer overlaying said electrical paths but free from said electrodes.
 12. The assembly of claim 11 including conductive coating overlaying said electrodes.
 13. A method for maintaining an appropriate level of patient awareness under anesthesia, the steps including: (A) providing at least one electrode assembly comprising: a flexible layer; a pattern of electrically conductive material, disposed upon one side of said flexible layer wherein said pattern contains at least two electrodes and is adapted to be connected to a signal receiving means; a non-conducting adhesive that electrically isolates at least one electrode from another electrode, but allows at least two electrodes to contact the tissue of said patient; (B) attaching said assembly to the face of said patient; (C) picking up a signal with the electrodes; (D) receiving the signal in a processing device through a signal receiving means; (E) processing the signal received from the electrodes to determine what facial expression the signal represents by comparing the signals from different electrodes, the signals being reflective of the patient's facial muscle tonus; (F) displaying the processed signal for viewing by an anesthesiologist on a display; (G) anesthetizing the patient with an initial dosage of anesthetic to create muscle relaxation in a desired level of awareness; and (H) controlling the patient's level of awareness.
 14. The awareness level method of claim 13 wherein said processing step includes detecting and filtering out artifacts unrepresentative of the patient's expression through the steps of: (i) detecting when an artifact generating device is in operation; (ii) quantifying the artifact generating device's effect on the signal as picked up by the facial muscle sensors; and (iii) subtracting from the signal the portion caused by the artifact; whereby the artifact has a reduced effect on the signal.
 15. The awareness level method of claim 13 including, after said attaching step, stimulating a nerve in the patient's face with an electrode.
 16. The awareness level maintenance method of claim 13 wherein said providing step includes: (i) providing a non-extensible material characterized by resisting linear distortion; (ii) applying through the mask means an electrically conductive material in pattern adapted to contact at appropriate sensing points the skin over at least one facial muscle group and to connect said electrically conductive material over said sensing points to a signal receiving means; (iii) coating with a non-conducting adhesive said non-extensible material except at areas that correlate with said electrodes contacting appropriate sensing points of said face; (iv) sealing the electrode assembly with a detachable cover layer opposite said flexible layer; (v) separating electrode assemblies from each other if said non-extensible material has more than one electrode assembly prepared upon said non-extensible material; and said attaching step includes detaching said cover layer before attaching said assembly to said face of said patient.
 17. The awareness level maintenance method of claim 16 wherein said non-conducting adhesive is applied through a second mask means adapted to prevent adhesive from covering said electrodes at points correlating to said sensing points.
 18. The awareness level maintenance method of claim 16 wherein said non-conducting adhesive is coated on said non-extensible material after releasable dots are placed over said electrically conductive material at points corresponding to said sensing points.
 19. The awareness level maintenance method of claim 16 wherein said non-conducting adhesive is applied as a preshaped pad adapted to cover the electrically conductive material except at points correlating to said sensing points.
 20. The awareness level method of claim 16 including, after said attaching step, stimulating a facial muscle nerve in the patient's face with an electrode.
 21. The awareness level maintenance method of claim 13 wherein said electrodes define a preconfigured array adapted to contact at appropriate sensing points the skin over one or more muscle groups of said race.
 22. The awareness level maintenance method of claim 15 wherein said electrodes define a preconfigured array adapted to contact at appropriate sensing points the skin over one or more muscle groups of said face.
 23. The awareness level maintenance method of claim 20, wherein said muscle groups are at least two of those among the corrogator, frontalis, zygomatic, orbicularis oculi, or masseter muscle groups.
 24. The awareness level maintenance method of claim 20 wherein said muscle groups are at least four of those among the corrogator, frontalis, zygomatic, orbicularis oculi, or masseter muscle groups.
 25. The awareness level maintenance method of claim 20 Therein said muscle groups are the corrogator, frontalis, zygomatic, orbicularis oculi, or masseter muscle groups.
 26. The awareness level method of claim 21 including, after said attaching step, stimulating a facial muscle nerve in at least one of said muscle groups.
 27. The awareness level method of claim 22 including, after said attaching step, stimulating a facial muscle nerve in the patient's face with an electrode.
 28. An apparatus for indicating the consciousness of a person, comprising, in combination: an array of facial muscle sensors adapted to generate sensor signals representing the simultaneous activity of at least four different facial muscle areas, each of which elicit distinctive patterns of facial expressions of the person; a sensor signal processor operatively coupled to the sensors to receive the sensor signals from the facial muscle sensors and, based on the sensor signals, automatically generate an output signal indicating the consciousness of the person; and wherein the sensor signal processor generates at least a portion of the output signal based on relative differences among the sensor signals and thereby the different activities of the different facial muscle areas represented by the sensor signals; and wherein the facial muscle sensors are surface electromyograms adapted to be physically attached the person's face in positions allowing the monitoring of the different facial muscles; and wherein said facial muscle areas are selected from among the frontalis area, the corrugator area, zygomatic area, the masseter area, and the orbilaris oculi area.
 29. A method of determining the consciousness of a person, the method comprising the steps of: (A) mounting at least four facial muscle activity sensors so that each activity sensor generates an activity signal based on the level of activity of a different facial muscle group on the person; and (B) processing said activity signals to generate a first output signal based on the summation of the activity signals for the sensed facial muscle groups; also including in step (B): processing said activity signals to generate a second output signal based on the differences between the activity signals for the sensed facial muscle groups; also including in step (B): filtering the activity signals to remove from the at least one output signal an artifact representing muscle activity caused by stimulus to the person not indicative of the person's consciousness; and wherein, in step (A) five facial muscle activity sensors are mounted, respectively, on the following five muscle areas: the frontalis area, the corrugator area, the zygomatic area, the masseter area, and the orbicularis oculi area. 